ceremony/docs/RUNNER-PROBES.md
cluade-reviewer-andresmgsl e61bb91476 docs(runner-probes): its own document, an arming procedure, and the evidence boundary made consistent (#202)
@codex-reviewer-andresmgsl's four gaps.

1. BRANCH UPDATED TO CURRENT MAIN. The commit's parent was pre-#204 dad99dd, so
   its green 22-file run did not contain the six test files and rules that
   landed with the sync. Merged main in — no rewrite — and re-verified against
   the 28-file suite the operator would actually receive.

2. WHO MAY RESET IT is now a section, and it says operator-owned until ruled
   otherwise, with content reset separated from archive/delete/admin. The
   access policy is set when the repo is created, which is the operator's step,
   so the two belong together. Flagged for @andres rather than assumed.

3. AN EXECUTABLE ARMING PROCEDURE replaces "install whatever the probe needs":
   fork ref and canonical SHA, caller stubs pinned to it, BOTH
   CEREMONY_SELF_REF carriers rewritten, the event invoked recorded by name,
   and what reset removes afterwards. It reuses the drill rehearsal's fork-ref
   pattern rather than inventing a floating pin, including its rule against
   ever creating a tag-shaped branch on heavy-duty/ceremony.

4. THE EVIDENCE CONTRADICTION IS RESOLVED. "Write results into an issue in this
   repo" and "no probe touches ceremony's board" could not both be followed in
   a file where "this repo" reads as ceremony. The job now writes raw results
   into the PROBE repo, and a human carries the issue URL and run number to the
   ceremony issue. The probe workflow holds no credential and no code path that
   can write to ceremony, which is what makes the two rules compatible.

Placement: the operational contract moves to docs/RUNNER-PROBES.md, with a
short cross-link in drills/README.md beside the disposal rule it excepts — the
exception stays visible where the dangerous habit lives, and neither document
grows a second top-level heading.

test/run.sh 28/28 on the updated branch; shellcheck 0.10.0, actionlint,
self-ref, marker, vendored and changelog-armed clean.

Refs #202
2026-08-05 13:40:28 +00:00

136 lines
6.7 KiB
Markdown

# Runner probes
**Not a drill.** A drill rehearses the release doors on a disposable repo and
ends. This is the opposite shape: one **standing** repo that exists so that
runner-only facts can be measured on demand, and it is **never archived**.
`heavy-duty/ceremony-runner-probe` — private, standing, reset between probes.
Ruled by the operator as option (A) of ceremony#202 (#5631).
## Why a standing repo, when drills are disposable
Some facts are only true inside Actions, under the token Actions injects, and
no local harness or PAT can reproduce them. The worked example is ceremony#192:
```
DELETE /issues/{n}/labels/{id} -> 500 under ${{ github.token }} in a workflow
DELETE /issues/{n}/labels/{id} -> 204 under a maintainer PAT, same call
```
A probe that runs anywhere else passes and proves nothing. Before this venue
existed the answer was "un-archive a drill repo", which was requested three
times in two days across two issues and never became anything — the three
drill repos (`ceremony-drill-0.4.1`, `-0.4.1-final`, `-191`) are all archived,
and each was minted for one probe and then wanted again.
## The disposal rule above does NOT apply here
The rehearsal section says the builder archives the scratch repo and the
operator deletes it. **That rule is for drills.** Archiving this repo defeats
its entire purpose, and it is the failure mode the three archived drill repos
demonstrate — each was archived correctly, by the rule, and each then had to be
un-archived or replaced.
So: never archive it, never delete it, and if you find it archived, un-archive
it rather than minting a fourth one.
## Standing it up is the operator's step
Bot identities cannot create repositories in `heavy-duty`. Measured
2026-08-05 with a fleet identity holding the `repo` scope:
```
POST /api/v1/orgs/heavy-duty/repos -> 403 "not allowed to create repository in organization"
POST /api/v1/user/repos -> 201 (personal namespace only)
```
This is the same shape as the drill delete: a deliberate permission boundary,
not a misconfiguration, and the same rule applies — do not retry it, and do not
work around it by putting the venue in a personal namespace, where the org's
runner and secrets do not reach. Ask the operator.
## Running a probe
1. Reset the repo to a clean state — the probe's own fixtures only, no
leftovers from the last one. A probe that inherits state is a probe whose
result you cannot attribute.
2. **Arm it against the candidate ref** (below), if the probe is about
ceremony's own code rather than about a bare API call.
3. **Run it as an Actions job under `${{ github.token }}`.** This is the whole
point of the venue and the one step that cannot be shortcut. A `curl` from a
laptop with a PAT answers a different question — see the 204/500 split
above — and a probe run that way is worse than no probe, because it produces
a confident wrong answer.
4. **The job writes its raw results into an issue in the PROBE repo**
`heavy-duty/ceremony-runner-probe` — not into ceremony. Logs age out;
ceremony#192's run 701 survived only because the job wrote its findings
into an issue it created.
5. **A human then records the probe issue's URL and the Actions run number on
the ceremony issue the probe serves.** That hop is deliberate and is the
whole of the boundary: the probe workflow holds no credential and no code
path that can write to `heavy-duty/ceremony`, so "the probe reports its
findings" and "the probe cannot touch the live board" stay compatible
rather than contradicting each other (@codex-reviewer-andresmgsl, #202
review).
## Arming a candidate ref
A probe that exercises ceremony's own machinery needs the candidate tree
reachable from a `uses:` line. The shape is the drill rehearsal's, reused
rather than reinvented (`drills/README.md` step 2):
1. **The candidate is a commit SHA, on a fork ref.** Push the candidate tree to
a fork under the identity running the probe —
`<identity>/ceremony@probe-<issue>` — and take its canonical SHA. Never
create a branch on `heavy-duty/ceremony` named like a tag: it shadows that
tag for every consumer until somebody remembers to delete it.
2. **Install `docs/CONSUMERS.md`'s caller stubs** in the probe repo, pinned to
that SHA — every `uses:` reference, not some of them.
3. **Rewrite `CEREMONY_SELF_REF` in the candidate itself** to the same
canonical SHA. A candidate carries the tag it has not created yet, so the
self-consumption checkout cannot resolve until it is rewritten. Both
carriers — `labels.yml` and `release.yml` — take the same value.
4. **Invoke the probe by the event it is about**, and record which: a
`workflow_dispatch` of the caller, or the real board event the probe is
testing. A probe that fires a different event than the one under test
proves something else.
5. **Record the fork ref, the rewritten pin, the workflow invoked and the run
number** in the probe repo's result issue. Those four are what make the
result reproducible; without the pin especially, a later reader cannot tell
which tree answered.
6. **Reset removes the candidate-specific fixtures**: the caller stubs, the
probe workflow and the result branch, so the next probe does not inherit a
pin it did not choose. The result *issue* stays — it is the evidence.
## Who may reset it
**Operator-owned until ruled otherwise.** #202's task 4 asks who may reset the
venue, and creating the repo is the operator's step, so the access policy is
his to set at the same time (@codex-reviewer-andresmgsl, #202 review).
Two levels, deliberately separated:
- **content reset** — deleting probe branches, workflows, fixtures and stale
result issues; the ordinary between-probes operation;
- **archive / delete / admin** — which is where the drill rule's damage came
from, and which no bot identity should hold here.
If fleet identities are given push access for content reset, this section
records that; until then, ask.
## What must never happen here
No probe touches `heavy-duty/ceremony`'s board. No labels, no comments, no
runs attributable to a probe. The venue exists so that the live board does not
have to be the test fixture.
## The probes this venue owes
- **ceremony#192** — that the repaired sweep actually lifts a label under the
workflow token, which is the half its acceptance criteria cannot get from
the hermetic contract tests.
- **ceremony#205** — whether `POST /actions/workflows/{file}/dispatches`
works on this instance with a valid ref and inputs. Measured so far:
`GET /actions/workflows` 404s and the dispatch route answers 500 rather than
a 4xx, which is not enough to port against.
- A 0.6.0 consumer exercise once ceremony#198 has merged.